This invention generally relates to the field of intravascular catheters, and more particularly to a dilatation catheter for percutaneous transluminal coronary angioplasty (PTCA) having perfusion capabilities.
PTCA is now one of the most widely used treatment modalities for heart disease. The procedure basically comprises advancing a dilatation catheter, having an inflatable dilatation balloon on the distal portion thereof, into the patient's coronary anatomy until the balloon is properly positioned across the lesion to be dilated. Once properly positioned, the dilatation balloon is inflated with liquid to a predetermined size at relatively high pressures to expand the arterial passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
Long term dilatation has many clinical advantages, including the elimination of sudden occlusion of an arterial passageway due to an arterial dissection. However, in order to effect long term dilatation some provision must be made to perfuse oxygenated blood distal to the catheter during the long term dilatation. One perfusion-type dilatation catheter which has met with a great deal of commercial success is the RX.RTM. Perfusion Dilatation Catheter which is available from the assignee of the present invention Advanced Cardiovascular Systems, Inc. The latter catheter has recently been replaced by a perfusion dilatation catheter sold by the present assignee under the trademark FlowTrack. These perfusion catheters have a plurality of perfusion ports in the wall forming at least part of the catheter body proximal to the balloon which are in fluid communication with a guidewire receiving inner lumen extending to the distal end of the catheter body. A plurality of perfusion ports are also preferably provided in the catheter body distal to the balloon which are also in fluid communication with the inner lumen extending to the distal end of the catheter body. When the balloon on the distal extremity of the dilatation catheter is inflated to dilate a stenosis, oxygenated blood in the artery or the aorta or both, depending upon the location of the dilatation catheter within the coronary anatomy, is forced to pass through the proximal perfusion ports, through the inner lumen of the catheter body and out the distal perfusion ports. This provides oxygenated blood downstream from the balloon while it is inflated to thereby prevent or minimize ischemic conditions in tissue distal to the catheter. The balloon can be inflated for long term dilatations with essentially no damage to tissue distal to the catheter. As is appreciated by those skilled in the art, tissue distal to a stenosis is frequently already in jeopardy due to ischemic conditions which may exist from the stenotic blockage. As a result, care should be exercised in sizing the perfusion ports and the inner lumen to ensure that there is adequate flow of oxygenated blood to tissue distal to the catheter. Providing larger perfusion ports can increase the blood flow but with larger perfusion ports there is a greater chance that a guidewire passing through the perfusion lumen can pass through a perfusion port. Providing a greater number of small perfusion ports increases the resistance to flow reducing the amount of blood which can flow through the catheter.
What has been needed is a perfusion type dilatation catheter which has one or more perfusion openings which can facilitate greater blood flow but which prevents guidewire excursions through the perfusion ports.